How to Build a Deck Ledger

Remove any steps and clear the area around the door of any sills or other impediments. Locate the rim joists, floor joists or similar supporting elements in the house. Find these in a basement or crawl space or look under the bottom row of siding. Mark those spots and determine a location for the ledger board.

Set the ledger an inch or so under the door threshold, low enough to allow for deck flooring, if there is a rim joist at that spot. Lower the ledger by a step, 7 to 9 inches, if necessary to find a rim joist for attachment. Remove the siding with a pry bar up to where the top of the ledger will be and mark a spot on each end of the planned deck width, an inch or so wider on each end than the actual deck.

Mark the height for the ledger board on each end. Snap a level chalk line between those points to outline the top of the ledger. Nail the ledger in place temporarily on each end with framing nails and a hammer and identify attachment points, through the ledger and into the house frame. Use one of two methods of attachment: bolts that go through the ledger and rim joist and are fastened with nuts inside a basement or crawl space, or lag bolts with screw points that screw through the ledger into the rim joist and floor joists where those intersect.

Drill holes with a power drill for attachment bolts. Drill holes through the rim joist into a basement or crawl space to use bolts with nuts or into the rim joist and into floor joists attached to the rim. Space holes to fit between floor joists if using bolts with nuts or 24 inches apart for lag bolts to screw into floor joists. Fasten bolts with a ratchet wrench with washers under the bolt heads to provide drainage between the ledger and the house sheathing.

Nail metal flashing to fit under the bottom of the house siding and over the top of the ledger. Use flashing wide enough to go at least 4 inches under the siding and over the top of the ledger. Make it slightly longer than the ledger. Cut that extension at the bend with tin snips, with one part to go under the siding. Bend the over part down over the end of the ledger. Replace siding down to the ledger and install any hangers or brackets to hold deck framing.